Method and device for generating stf signals by means of binary sequence in wireless lan system

ABSTRACT

Provided are method and device for generating STF signals which can be used in a wireless LAN system. STF signals are comprised in a field which is used for improving AGC estimation of MIMO transmission. Some of the STF signals are used for uplink transmission and can be used for an uplink MU PPDU transmitted from a plurality of STAs. The provided STF signals are, for example, used for an 80+80 MHz or 160 MHz band and can be generated on the basis of a sequence in which a preset M sequence is repeated. The preset M sequence can be a 15-bit length binary sequence.

BACKGROUND OF THE INVENTION Field of the Invention

This specification relates to a method for generating a sequence for atraining field in a wireless LAN system and, most particularly, to amethod and apparatus for generating a short training field (STF)sequence that can be used in multiple bands in a wireless LAN system.

Related Art

Discussion for a next-generation wireless local area network (WLAN) isin progress. In the next-generation WLAN, an object is to 1) improve aninstitute of electronic and electronics engineers (IEEE) 802.11 physical(PHY) layer and a medium access control (MAC) layer in bands of 2.4 GHzand 5 GHz, 2) increase spectrum efficiency and area throughput, 3)improve performance in actual indoor and outdoor environments such as anenvironment in which an interference source exists, a denseheterogeneous network environment, and an environment in which a highuser load exists, and the like.

An environment which is primarily considered in the next-generation WLANis a dense environment in which access points (APs) and stations (STAs)are a lot and under the dense environment, improvement of the spectrumefficiency and the area throughput is discussed. Further, in thenext-generation WLAN, in addition to the indoor environment, in theoutdoor environment which is not considerably considered in the existingWLAN, substantial performance improvement is concerned.

In detail, scenarios such as wireless office, smart home, stadium,Hotspot, and building/apartment are largely concerned in thenext-generation WLAN and discussion about improvement of systemperformance in a dense environment in which the APs and the STAs are alot is performed based on the corresponding scenarios.

In the next-generation WLAN, improvement of system performance in anoverlapping basic service set (OBSS) environment and improvement ofoutdoor environment performance, and cellular offloading are anticipatedto be actively discussed rather than improvement of single linkperformance in one basic service set (BSS). Directionality of thenext-generation means that the next-generation WLAN gradually has atechnical scope similar to mobile communication. When a situation isconsidered, in which the mobile communication and the WLAN technologyhave been discussed in a small cell and a direct-to-direct (D2D)communication area in recent years, technical and business convergenceof the next-generation WLAN and the mobile communication is predicted tobe further active.

SUMMARY OF THE INVENTION

This specification proposes a method and apparatus for configuring asequence that is used for a training field in a wireless LAN system.

An example of this specification proposes a solution for enhancing theproblems in the sequence for the STF field that is presented in therelated art.

An example of the present specification proposes a transmission methodapplicable to a wireless LAN system, more particularly, proposes amethod and an apparatus of generating a short training field (STF)signal for supporting at least any one of a plurality of frequency bandssupported in the wireless LAN system.

A transmitting apparatus according to the present specification,generates the STF signal corresponding to a first frequency band, andtransmits a PPDU (physical protocol data unit) including the STF signal.

The STF signal corresponding to the first frequency band may begenerated based on a sequence in which a preset M sequence is repeated,and

The repeated sequence may be defined as a {M, −1, M, −1, −M, −1, M, 0,−M, 1, M, 1, −M, 1, −M, 0, −M, 1, −M, 1, M, 1, −M, 0, −M, 1, M, 1, −M,1, −M}*(1+j)/sqrt(2).

The predetermined M sequence may be a binary sequence of a length having15 bits. In this case, the M sequence may be M={−1, −1, −1, 1, 1, 1, −1,1, 1, 1, −1, 1, 1, −1, 1}.

According to an example of this specification, a method for generating aSTF signal that can be used in the wireless LAN system is proposedherein.

The method for generating a STF signal that is proposed in the exampleof this specification resolves the problems presented in the relatedart.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual view illustrating the structure of a wirelesslocal area network (WLAN).

FIG. 2 is a diagram illustrating an example of a PPDU used in an IEEEstandard.

FIG. 3 is a diagram illustrating an example of an HE PDDU.

FIG. 4 is a diagram illustrating a layout of resource units (RUs) usedin a band of 20 MHz.

FIG. 5 is a diagram illustrating a layout of resource units (RUs) usedin a band of 40 MHz.

FIG. 6 is a diagram illustrating a layout of resource units (RUs) usedin a band of 80 MHz.

FIG. 7 is a diagram illustrating another example of the HE PPDU.

FIG. 8 is a block diagram illustrating one example of HE-SIG-B accordingto an embodiment.

FIG. 9 illustrates an example of a trigger frame.

FIG. 10 illustrates an example of a common information field.

FIG. 11 illustrates an example of a sub-field being included in a peruser information field.

FIG. 12 is a block diagram illustrating an example of an uplink MU PPDU.

FIG. 13 illustrates a 1×HE-STF tone in a per-channel PPDU transmissionaccording to an exemplary embodiment of the present invention.

FIG. 14 illustrates a 2×HE-STF tone in a per-channel PPDU transmissionaccording to an exemplary embodiment of the present invention.

FIG. 15 illustrates an example of repeating an M sequence.

FIG. 16 is an example specifying the repeated structure of FIG. 15 inmore detail.

FIG. 17 illustrates an example of repeating an M sequence.

FIG. 18 is an example specifying the repeated structure of FIG. 17 inmore detail.

FIG. 19 is a diagram illustrating the above-mentioned example of PAPRexpressed in RU units used in the 80+80/160 MHz band.

FIG. 20 is a diagram illustrating the above-mentioned example of PAPRexpressed in RU units used in the 80+80/160 MHz band.

FIG. 21 is a diagram illustrating the above-mentioned example of PAPRexpressed in RU units used in the 80+80/160 MHz band.

FIG. 22 is a diagram illustrating the above-mentioned example of PAPRexpressed in RU units used in the 80+80/160 MHz band.

FIG. 23 is a diagram illustrating the above-mentioned example of PAPRexpressed in RU units used in the 80+80/160 MHz band.

FIG. 24 is a diagram illustrating the above-mentioned example of PAPRexpressed in RU units used in the 80+80/160 MHz band.

FIG. 25 is a diagram illustrating the above-mentioned example of PAPRexpressed in RU units used in the 80+80/160 MHz band.

FIG. 26 is a diagram illustrating the above-mentioned example of PAPRexpressed in RU units used in the 80+80/160 MHz band.

FIG. 27 is a diagram illustrating the above-mentioned example of PAPRexpressed in RU units used in the 80+80/160 MHz band.

FIG. 28 is a diagram illustrating the above-mentioned example of PAPRexpressed in RU units used in the 80+80/160 MHz band.

FIG. 29 is a diagram illustrating the above-mentioned example of PAPRexpressed in RU units used in the 80+80/160 MHz band.

FIG. 30 is a diagram illustrating the above-mentioned example of PAPRexpressed in RU units used in the 80+80/160 MHz band.

FIG. 31 is a diagram illustrating the above-mentioned example of PAPRexpressed in RU units used in the 80+80/160 MHz band.

FIG. 32 is a diagram illustrating the above-mentioned example of PAPRexpressed in RU units used in the 80+80/160 MHz band.

FIG. 33 is a diagram illustrating the above-mentioned example of PAPRexpressed in RU units used in the 80+80/160 MHz band.

FIG. 34 is a procedure flow chart to which the above-described examplecan be applied.

FIG. 35 is a block diagram showing a wireless device to which theexemplary embodiment of the present invention can be applied.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

FIG. 1 is a conceptual view illustrating the structure of a wirelesslocal area network (WLAN).

An upper part of FIG. 1 illustrates the structure of an infrastructurebasic service set (BSS) of institute of electrical and electronicengineers (IEEE) 802.11.

Referring the upper part of FIG. 1, the wireless LAN system may includeone or more infrastructure BSSs 100 and 105 (hereinafter, referred to asBSS). The BSSs 100 and 105 as a set of an AP and an STA such as anaccess point (AP) 125 and a station (STA1) 100-1 which are successfullysynchronized to communicate with each other are not concepts indicatinga specific region. The BSS 105 may include one or more STAs 105-1 and105-2 which may be joined to one AP 130.

The BSS may include at least one STA, APs providing a distributionservice, and a distribution system (DS) 110 connecting multiple APs.

The distribution system 110 may implement an extended service set (ESS)140 extended by connecting the multiple BSSs 100 and 105. The ESS 140may be used as a term indicating one network configured by connectingone or more APs 125 or 230 through the distribution system 110. The APincluded in one ESS 140 may have the same service set identification(SSID).

A portal 120 may serve as a bridge which connects the wireless LANnetwork (IEEE 802.11) and another network (e.g., 802.X).

In the BSS illustrated in the upper part of FIG. 1, a network betweenthe APs 125 and 130 and a network between the APs 125 and 130 and theSTAs 100-1, 105-1, and 105-2 may be implemented. However, the network isconfigured even between the STAs without the APs 125 and 130 to performcommunication. A network in which the communication is performed byconfiguring the network even between the STAs without the APs 125 and130 is defined as an Ad-Hoc network or an independent basic service set(IBSS).

A lower part of FIG. 1 illustrates a conceptual view illustrating theIBSS.

Referring to the lower part of FIG. 1, the IBSS is a BSS that operatesin an Ad-Hoc mode. Since the IBSS does not include the access point(AP), a centerized management entity that performs a management functionat the center does not exist. That is, in the IBSS, STAs 150-1, 150-2,150-3, 155-4, and 155-5 are managed by a distributed manner. In theIBSS, all STAs 150-1, 150-2, 150-3, 155-4, and 155-5 may be constitutedby movable STAs and are not permitted to access the DS to constitute aself-contained network.

The STA as a predetermined functional medium that includes a mediumaccess control (MAC) that follows a regulation of an Institute ofElectrical and Electronics Engineers (IEEE) 802.11 standard and aphysical layer interface for a radio medium may be used as a meaningincluding all of the APs and the non-AP stations (STAs).

The STA may be called various a name such as a mobile terminal, awireless device, a wireless transmit/receive unit (WTRU), user equipment(UE), a mobile station (MS), a mobile subscriber unit, or just a user.

Meanwhile, the term user may be used in diverse meanings, for example,in wireless LAN communication, this term may be used to signify a STAparticipating in uplink MU MIMO and/or uplink OFDMA transmission.However, the meaning of this term will not be limited only to this.

FIG. 2 is a diagram illustrating an example of a PPDU used in an IEEEstandard.

As illustrated in FIG. 2, various types of PHY protocol data units(PPDUs) may be used in a standard such as IEEE a/g/n/ac, etc. In detail,LTF and STF fields include a training signal, SIG-A and SIG-B includecontrol information for a receiving station, and a data field includesuser data corresponding to a PSDU.

In the embodiment, an improved technique is provided, which isassociated with a signal (alternatively, a control information field)used for the data field of the PPDU. The signal provided in theembodiment may be applied onto high efficiency PPDU (HE PPDU) accordingto an IEEE 802.11ax standard. That is, the signal improved in theembodiment may be HE-SIG-A and/or HE-SIG-B included in the HE PPDU. TheHE-SIG-A and the HE-SIG-B may be represented even as the SIG-A andSIG-B, respectively. However, the improved signal proposed in theembodiment is not particularly limited to an HE-SIG-A and/or HE-SIG-Bstandard and may be applied to control/data fields having various names,which include the control information in a wireless communication systemtransferring the user data.

FIG. 3 is a diagram illustrating an example of an HE PDDU.

The control information field provided in the embodiment may be theHE-SIG-B included in the HE PPDU. The HE PPDU according to FIG. 3 is oneexample of the PPDU for multiple users and only the PPDU for themultiple users may include the HE-SIG-B and the corresponding HE SIG-Bmay be omitted in a PPDU for a single user.

As illustrated in FIG. 3, the HE-PPDU for multiple users (MUs) mayinclude a legacy-short training field (L-STF), a legacy-long trainingfield (L-LTF), a legacy-signal (L-SIG), a high efficiency-signal A(HE-SIG A), a high efficiency-signal-B (HE-SIG B), a highefficiency-short training field (HE-STF), a high efficiency-longtraining field (HE-LTF), a data field (alternatively, an MAC payload),and a packet extension (PE) field. The respective fields may betransmitted during an illustrated time period (that is, 4 or 8 μs).

More detailed description of the respective fields of FIG. 3 will bemade below.

FIG. 4 is a diagram illustrating a layout of resource units (RUs) usedin a band of 20 MHz.

As illustrated in FIG. 4, resource units (RUs) corresponding to tone(that is, subcarriers) of different numbers are used to constitute somefields of the HE-PPDU. For example, the resources may be allocated bythe unit of the RU illustrated for the HE-STF, the HE-LTF, and the datafield.

As illustrated in an uppermost part of FIG. 4, 26 units (that is, unitscorresponding to 26 tones). 6 tones may be used as a guard band in aleftmost band of the 20 MHz band and 5 tones may be used as the guardband in a rightmost band of the 20 MHz band. Further, 7 DC tones may beinserted into a center band, that is, a DC band and a 26-unitcorresponding to each 13 tones may be present at left and right sides ofthe DC band. The 26-unit, a 52-unit, and a 106-unit may be allocated toother bands. Each unit may be allocated for a receiving station, thatis, a user.

Meanwhile, the RU layout of FIG. 4 may be used even in a situation for asingle user (SU) in addition to the multiple users (MUs) and in thiscase, as illustrated in a lowermost part of FIG. 4, one 242-unit may beused and in this case, three DC tones may be inserted.

In one example of FIG. 4, RUs having various sizes, that is, a 26-RU, a52-RU, a 106-RU, a 242-RU, and the like are proposed, and as a result,since detailed sizes of the RUs may extend or increase, the embodimentis not limited to a detailed size (that is, the number of correspondingtones) of each RU.

FIG. 5 is a diagram illustrating a layout of resource units (RUs) usedin a band of 40 MHz.

Similarly to a case in which the RUs having various RUs are used in oneexample of FIG. 4, 26-RU, 52-RU, 106-RU, 242-RU, 484-RU, and the likemay be used even in one example of FIG. 5. Further, 5 DC tones may beinserted into a center frequency, 12 tones may be used as the guard bandin the leftmost band of the 40 MHz band and 11 tones may be used as theguard band in the rightmost band of the 40 MHz band.

In addition, as illustrated in FIG. 5, when the RU layout is used forthe single user, the 484-RU may be used. That is, the detailed number ofRUs may be modified similarly to one example of FIG. 4.

FIG. 6 is a diagram illustrating a layout of resource units (RUs) usedin a band of 80 MHz.

Similarly to a case in which the RUs having various RUs are used in oneexample of each of FIG. 4 or 5, 26-RU, 52-RU, 106-RU, 242-RU, 484-RU,and the like may be used even in one example of FIG. 6. Further, 7 DCtones may be inserted into the center frequency, 12 tones may be used asthe guard band in the leftmost band of the 80 MHz band and 11 tones maybe used as the guard band in the rightmost band of the 80 MHz band. Inaddition, the 26-RU may be used, which uses 13 tones positioned at eachof left and right sides of the DC band.

Moreover, as illustrated in FIG. 6, when the RU layout is used for thesingle user, 996-RU may be used and in this case, 5 DC tones may beinserted. Meanwhile, the detailed number of RUs may be modifiedsimilarly to one example of each of FIG. 4 or 5.

FIG. 7 is a diagram illustrating another example of the HE PPDU.

A block illustrated in FIG. 7 is another example of describing theHE-PPDU block of FIG. 3 in terms of a frequency.

An illustrated L-STF 700 may include a short training orthogonalfrequency division multiplexing (OFDM) symbol. The L-STF 700 may be usedfor frame detection, automatic gain control (AGC), diversity detection,and coarse frequency/time synchronization.

An L-LTF 710 may include a long training orthogonal frequency divisionmultiplexing (OFDM) symbol. The L-LTF 710 may be used for finefrequency/time synchronization and channel prediction.

An L-SIG 720 may be used for transmitting control information. The L-SIG720 may include information regarding a data rate and a data length.Further, the L-SIG 720 may be repeatedly transmitted. That is, a newformat, in which the L-SIG 720 is repeated (for example, may be referredto as R-LSIG) may be configured.

An HE-SIG-A 730 may include the control information common to thereceiving station.

In detail, the HE-SIG-A 730 may include information on 1) a DL/ULindicator, 2) a BSS color field indicating an identify of a BSS, 3) afield indicating a remaining time of a current TXOP period, 4) abandwidth field indicating at least one of 20, 40, 80, 160 and 80+80MHz, 5) a field indicating an MCS technique applied to the HE-SIG-B, 6)an indication field regarding whether the HE-SIG-B is modulated by adual subcarrier modulation technique for MCS, 7) a field indicating thenumber of symbols used for the HE-SIG-B, 8) a field indicating whetherthe HE-SIG-B is configured for a full bandwidth MIMO transmission, 9) afield indicating the number of symbols of the HE-LTF, 10) a fieldindicating the length of the HE-LTF and a CP length, 11) a fieldindicating whether an OFDM symbol is present for LDPC coding, 12) afield indicating control information regarding packet extension (PE),13) a field indicating information on a CRC field of the HE-SIG-A, andthe like. A detailed field of the HE-SIG-A may be added or partiallyomitted. Further, some fields of the HE-SIG-A may be partially added oromitted in other environments other than a multi-user (MU) environment.

An HE-SIG-B 740 may be included only in the case of the PPDU for themultiple users (MUs) as described above. Principally, an HE-SIG-A 750 oran HE-SIG-B 760 may include resource allocation information(alternatively, virtual resource allocation information) for at leastone receiving STA.

FIG. 8 is a block diagram illustrating one example of HE-SIG-B accordingto an embodiment.

As illustrated in FIG. 8, the HE-SIG-B field includes a common field ata frontmost part and the corresponding common field is separated from afield which follows therebehind to be encoded. That is, as illustratedin FIG. 8, the HE-SIG-B field may include a common field including thecommon control information and a user-specific field includinguser-specific control information. In this case, the common field mayinclude a CRC field corresponding to the common field, and the like andmay be coded to be one BCC block. The user-specific field subsequentthereafter may be coded to be one BCC block including the “user-specificfield” for 2 users and a CRC field corresponding thereto as illustratedin FIG. 8.

A previous field of the HE-SIG-B 740 may be transmitted in a duplicatedform on an MU PPDU. In the case of the HE-SIG-B 740, the HE-SIG-B 740transmitted in some frequency band (e.g., a fourth frequency band) mayeven include control information for a data field corresponding to acorresponding frequency band (that is, the fourth frequency band) and adata field of another frequency band (e.g., a second frequency band)other than the corresponding frequency band. Further, a format may beprovided, in which the HE-SIG-B 740 in a specific frequency band (e.g.,the second frequency band) is duplicated with the HE-SIG-B 740 ofanother frequency band (e.g., the fourth frequency band). Alternatively,the HE-SIG B 740 may be transmitted in an encoded form on alltransmission resources. A field after the HE-SIG B 740 may includeindividual information for respective receiving STAs receiving the PPDU.

The HE-STF 750 may be used for improving automatic gain controlestimation in a multiple input multiple output (MIMO) environment or anOFDMA environment.

The HE-LTF 760 may be used for estimating a channel in the MIMOenvironment or the OFDMA environment.

The size of fast Fourier transform (FFT)/inverse fast Fourier transform(IFFT) applied to the HE-STF 750 and the field after the HE-STF 750, andthe size of the FFT/IFFT applied to the field before the HE-STF 750 maybe different from each other. For example, the size of the FFT/IFFTapplied to the HE-STF 750 and the field after the HE-STF 750 may be fourtimes larger than the size of the FFT/IFFT applied to the field beforethe HE-STF 750.

For example, when at least one field of the L-STF 700, the L-LTF 710,the L-SIG 720, the HE-SIG-A 730, and the HE-SIG-B 740 on the PPDU ofFIG. 7 is referred to as a first field, at least one of the data field770, the HE-STF 750, and the HE-LTF 760 may be referred to as a secondfield. The first field may include a field associated with a legacysystem and the second field may include a field associated with an HEsystem. In this case, the fast Fourier transform (FFT) size and theinverse fast Fourier transform (IFFT) size may be defined as a sizewhich is N (N is a natural number, e.g., N=1, 2, and 4) times largerthan the FFT/IFFT size used in the legacy wireless LAN system. That is,the FFT/IFFT having the size may be applied, which is N (=4) timeslarger than the first field of the HE PPDU. For example, 256 FFT/IFFTmay be applied to a bandwidth of 20 MHz, 512 FFT/IFFT may be applied toa bandwidth of 40 MHz, 1024 FFT/IFFT may be applied to a bandwidth of 80MHz, and 2048 FFT/IFFT may be applied to a bandwidth of continuous 160MHz or discontinuous 160 MHz.

In other words, a subcarrier space/subcarrier spacing may have a sizewhich is 1/N times (N is the natural number, e.g., N=4, the subcarrierspacing is set to 78.125 kHz) the subcarrier space used in the legacywireless LAN system. That is, subcarrier spacing having a size of 312.5kHz, which is legacy subcarrier spacing may be applied to the firstfield of the HE PPDU and a subcarrier space having a size of 78.125 kHzmay be applied to the second field of the HE PPDU.

Alternatively, an IDFT/DFT period applied to each symbol of the firstfield may be expressed to be N (=4) times shorter than the IDFT/DFTperiod applied to each data symbol of the second field. That is, theIDFT/DFT length applied to each symbol of the first field of the HE PPDUmay be expressed as 3.2 ρs and the IDFT/DFT length applied to eachsymbol of the second field of the HE PPDU may be expressed as 3.2 μs*4(=12.8 μs). The length of the OFDM symbol may be a value acquired byadding the length of a guard interval (GI) to the IDFT/DFT length. Thelength of the GI may have various values such as 0.4 μs, 0.8 μs, 1.6 μs,2.4 μs, and 3.2 μs.

The characteristic that the size of the FFT/IFFT being applied to theHE-STF 750 and the fields after the HE-STF 750 can be diverselyconfigured may be applied to a downlink PPDU and/or an uplink PPDU. Morespecifically, such characteristic may be applied to the PPDU shown inFIG. 7 or to an uplink MU PPDU, which will be described later on.

For simplicity in the description, in FIG. 7, it is expressed that afrequency band used by the first field and a frequency band used by thesecond field accurately coincide with each other, but both frequencybands may not completely coincide with each other, in actual. Forexample, a primary band of the first field (L-STF, L-LTF, L-SIG,HE-SIG-A, and HE-SIG-B) corresponding to the first frequency band may bethe same as the most portions of a frequency band of the second field(HE-STF, HE-LTF, and Data), but boundary surfaces of the respectivefrequency bands may not coincide with each other. As illustrated inFIGS. 4 to 6, since multiple null subcarriers, DC tones, guard tones,and the like are inserted during arranging the RUs, it may be difficultto accurately adjust the boundary surfaces.

The user (e.g., a receiving station) may receive the HE-SIG-A 730 andmay be instructed to receive the downlink PPDU based on the HE-SIG-A730. In this case, the STA may perform decoding based on the FFT sizechanged from the HE-STF 750 and the field after the HE-STF 750. On thecontrary, when the STA may not be instructed to receive the downlinkPPDU based on the HE-SIG-A 730, the STA may stop the decoding andconfigure a network allocation vector (NAV). A cyclic prefix (CP) of theHE-STF 750 may have a larger size than the CP of another field and theduring the CP period, the STA may perform the decoding for the downlinkPPDU by changing the FFT size.

Hereinafter, in the embodiment of the present invention, data(alternatively, or a frame) which the AP transmits to the STA may beexpressed as a terms called downlink data (alternatively, a downlinkframe) and data (alternatively, a frame) which the STA transmits to theAP may be expressed as a term called uplink data (alternatively, anuplink frame). Further, transmission from the AP to the STA may beexpressed as downlink transmission and transmission from the STA to theAP may be expressed as a term called uplink transmission.

In addition, a PHY protocol data unit (PPDU), a frame, and datatransmitted through the downlink transmission may be expressed as termssuch as a downlink PPDU, a downlink frame, and downlink data,respectively. The PPDU may be a data unit including a PPDU header and aphysical layer service data unit (PSDU) (alternatively, a MAC protocoldata unit (MPDU)). The PPDU header may include a PHY header and a PHYpreamble and the PSDU (alternatively, MPDU) may include the frame orindicate the frame (alternatively, an information unit of the MAC layer)or be a data unit indicating the frame. The PHY header may be expressedas a physical layer convergence protocol (PLCP) header as another termand the PHY preamble may be expressed as a PLCP preamble as anotherterm.

Further, a PPDU, a frame, and data transmitted through the uplinktransmission may be expressed as terms such as an uplink PPDU, an uplinkframe, and uplink data, respectively.

In the wireless LAN system to which the embodiment of the presentdescription is applied, the whole bandwidth may be used for downlinktransmission to one STA and uplink transmission to one STA. Further, inthe wireless LAN system to which the embodiment of the presentdescription is applied, the AP may perform downlink (DL) multi-user (MU)transmission based on multiple input multiple output (MU MIMO) and thetransmission may be expressed as a term called DL MU MIMO transmission.

In addition, in the wireless LAN system according to the embodiment, anorthogonal frequency division multiple access (OFDMA) based transmissionmethod is preferably supported for the uplink transmission and/ordownlink transmission. That is, data units (e.g., RUs) corresponding todifferent frequency resources are allocated to the user to performuplink/downlink communication. In detail, in the wireless LAN systemaccording to the embodiment, the AP may perform the DL MU transmissionbased on the OFDMA and the transmission may be expressed as a termcalled DL MU OFDMA transmission. When the DL MU OFDMA transmission isperformed, the AP may transmit the downlink data (alternatively, thedownlink frame and the downlink PPDU) to the plurality of respectiveSTAs through the plurality of respective frequency resources on anoverlapped time resource. The plurality of frequency resources may be aplurality of subbands (alternatively, sub channels) or a plurality ofresource units (RUs). The DL MU OFDMA transmission may be used togetherwith the DL MU MIMO transmission. For example, the DL MU MIMOtransmission based on a plurality of space-time streams (alternatively,spatial streams) may be performed on a specific subband (alternatively,sub channel) allocated for the DL MU OFDMA transmission.

Further, in the wireless LAN system according to the embodiment, uplinkmulti-user (UL MU) transmission in which the plurality of STAs transmitsdata to the AP on the same time resource may be supported. Uplinktransmission on the overlapped time resource by the plurality ofrespective STAs may be performed on a frequency domain or a spatialdomain.

When the uplink transmission by the plurality of respective STAs isperformed on the frequency domain, different frequency resources may beallocated to the plurality of respective STAs as uplink transmissionresources based on the OFDMA. The different frequency resources may bedifferent subbands (alternatively, sub channels) or different resourcesunits (RUs). The plurality of respective STAs may transmit uplink datato the AP through different frequency resources. The transmission methodthrough the different frequency resources may be expressed as a termcalled a UL MU OFDMA transmission method.

When the uplink transmission by the plurality of respective STAs isperformed on the spatial domain, different time-space streams(alternatively, spatial streams) may be allocated to the plurality ofrespective STAs and the plurality of respective STAs may transmit theuplink data to the AP through the different time-space streams. Thetransmission method through the different spatial streams may beexpressed as a term called a UL MU MIMO transmission method.

The UL MU OFDMA transmission and the UL MU MIMO transmission may be usedtogether with each other. For example, the UL MU MIMO transmission basedon the plurality of space-time streams (alternatively, spatial streams)may be performed on a specific subband (alternatively, sub channel)allocated for the UL MU OFDMA transmission.

In the legacy wireless LAN system which does not support the MU OFDMAtransmission, a multi-channel allocation method is used for allocating awider bandwidth (e.g., a 20 MHz excess bandwidth) to one terminal. Whena channel unit is 20 MHz, multiple channels may include a plurality of20 MHz-channels. In the multi-channel allocation method, a primarychannel rule is used to allocate the wider bandwidth to the terminal.When the primary channel rule is used, there is a limit for allocatingthe wider bandwidth to the terminal. In detail, according to the primarychannel rule, when a secondary channel adjacent to a primary channel isused in an overlapped BSS (OBSS) and is thus busy, the STA may useremaining channels other than the primary channel. Therefore, since theSTA may transmit the frame only to the primary channel, the STA receivesa limit for transmission of the frame through the multiple channels.That is, in the legacy wireless LAN system, the primary channel ruleused for allocating the multiple channels may be a large limit inobtaining a high throughput by operating the wider bandwidth in acurrent wireless LAN environment in which the OBSS is not small.

In order to solve the problem, in the embodiment, a wireless LAN systemis disclosed, which supports the OFDMA technology. That is, the OFDMAtechnique may be applied to at least one of downlink and uplink.Further, the MU-MIMO technique may be additionally applied to at leastone of downlink and uplink. When the OFDMA technique is used, themultiple channels may be simultaneously used by not one terminal butmultiple terminals without the limit by the primary channel rule.Therefore, the wider bandwidth may be operated to improve efficiency ofoperating a wireless resource.

As described above, in case the uplink transmission performed by each ofthe multiple STAs (e.g., non-AP STAs) is performed within the frequencydomain, the AP may allocate different frequency resources respective toeach of the multiple STAs as uplink transmission resources based onOFDMA. Additionally, as described above, the frequency resources eachbeing different from one another may correspond to different subbands(or sub-channels) or different resource units (RUs).

The different frequency resources respective to each of the multipleSTAs are indicated through a trigger frame.

FIG. 9 illustrates an example of a trigger frame. The trigger frame ofFIG. 9 allocates resources for Uplink Multiple-User (MU) transmissionand may be transmitted from the AP. The trigger frame may be configuredas a MAC frame and may be included in the PPDU. For example, the triggerframe may be transmitted through the PPDU shown in FIG. 3, through thelegacy PPDU shown in FIG. 2, or through a certain PPDU, which is newlydesigned for the corresponding trigger frame. In case the trigger frameis transmitted through the PPDU of FIG. 3, the trigger frame may beincluded in the data field shown in the drawing.

Each of the fields shown in FIG. 9 may be partially omitted, or otherfields may be added. Moreover, the length of each field may be varieddifferently as shown in the drawing.

A Frame Control field 910 shown in FIG. 9 may include informationrelated to a version of the MAC protocol and other additional controlinformation, and a Duration field 920 may include time information forconfiguring a NAV or information related to an identifier (e.g., AID) ofthe user equipment.

Additionally, a RA field 930 may include address information of areceiving STA of the corresponding trigger frame, and this field mayalso be omitted as required. A TA field 940 may include addressinformation of the STA (e.g., AP) transmitting the corresponding triggerframe, and a common information field 950 may include common controlinformation that is applied to the receiving STA receiving thecorresponding trigger frame.

FIG. 10 illustrates an example of a common information field. Among thesub-fields of FIG. 10, some may be omitted, and other additionalsub-fields may also be added. Additionally, the length of each of thesub-fields shown in the drawing may be varied.

As shown in the drawing, the Length field 1010 may be given that samevalue as the Length field of the L-SIG field of the uplink PPDU, whichis transmitted in response to the corresponding trigger frame, and theLength field of the L-SIG field of the uplink PPDU indicates the lengthof the uplink PPDU. As a result, the Length field 1010 of the triggerframe may be used for indicating the length of its respective uplinkPPDU.

Additionally, a Cascade Indicator field 1020 indicates whether or not acascade operation is performed. The cascade operation refers to adownlink MU transmission and an uplink MU transmission being performedsimultaneously within the same TXOP. More specifically, this refers to acase when a downlink MU transmission is first performed, and, then,after a predetermined period of time (e.g., SIFS), an uplink MUtransmission is performed. During the cascade operation, only onetransmitting device performing downlink communication (e.g., AP) mayexist, and multiple transmitting devices performing uplink communication(e.g., non-AP) may exist.

A CS Request field 1030 indicates whether or not the status or NAV of awireless medium is required to be considered in a situation where areceiving device that has received the corresponding trigger frametransmits the respective uplink PPDU.

A HE-SIG-A information field 1040 may include information controllingthe content of a SIG-A field (i.e., HE-SIG-A field) of an uplink PPDU,which is being transmitted in response to the corresponding triggerframe.

A CP and LTF type field 1050 may include information on a LTF length anda CP length of the uplink PPDU being transmitted in response to thecorresponding trigger frame. A trigger type field 1060 may indicate apurpose for which the corresponding trigger frame is being used, e.g.,general triggering, triggering for beamforming, and so on, a request fora Block ACK/NACK, and so on.

Meanwhile, the remaining description on FIG. 9 will be additionallyprovided as described below.

It is preferable that the trigger frame includes per user informationfields 960#1 to 960#N corresponding to the number of receiving STAsreceiving the trigger frame of FIG. 9. The per user information fieldmay also be referred to as a “RU Allocation field”.

Additionally, the trigger frame of FIG. 9 may include a Padding field970 and a Sequence field 980.

It is preferable that each of the per user information fields 960#1 to960#N shown in FIG. 9 further includes multiple sub-fields.

FIG. 11 illustrates an example of a sub-field being included in a peruser information field. Among the sub-fields of FIG. 11, some may beomitted, and other additional sub-fields may also be added.Additionally, the length of each of the sub-fields shown in the drawingmay be varied.

A User Identifier field 1110 indicates an identifier of an STA (i.e.,receiving STA) to which the per user information corresponds, and anexample of the identifier may correspond to all or part of the AID.

Additionally, a RU Allocation field 1120 may be included in thesub-field of the per user information field. More specifically, in casea receiving STA, which is identified by the User Identifier field 1110,transmits an uplink PPDU in response to the trigger frame of FIG. 9, thecorresponding uplink PPDU is transmitted through the RU, which isindicated by the RU Allocation field 1120. In this case, it ispreferable that the RU that is being indicated by the RU Allocationfield 1120 corresponds to the RU shown in FIG. 4, FIG. 5, and FIG. 6.

The sub-field of FIG. 11 may include a Coding Type field 1130. TheCoding Type field 1130 may indicate a coding type of the uplink PPDUbeing transmitted in response to the trigger frame of FIG. 9. Forexample, in case BBC coding is applied to the uplink PPDU, the CodingType field 1130 may be set to ‘1’, and, in case LDPC coding is appliedto the uplink PPDU, the Coding Type field 1130 may be set to ‘0’.

Additionally, the sub-field of FIG. 11 may include a MCS field 1140. TheMCS field 1140 may indicate a MCS scheme being applied to the uplinkPPDU that is transmitted in response to the trigger frame of FIG. 9. Forexample, in case BBC coding is applied to the uplink PPDU, the CodingType field 1130 may be set to ‘1’, and, in case LDPC coding is appliedto the uplink PPDU, the Coding Type field 1130 may be set to ‘0’.

FIG. 12 is a block diagram illustrating an example of an uplink MU PPDU.The uplink MU PPDU of FIG. 12 may be transmitted in response to theabove-described trigger frame.

As shown in the drawing, the PPDU of FIG. 12 includes diverse fields,and the fields included herein respectively correspond to the fieldsshown in FIG. 2, FIG. 3, and FIG. 7. Meanwhile, as shown in the drawing,the uplink PPDU of FIG. 12 may not include a HE-SIG-B field and may onlyinclude a HE-SIG-A field.

FIG. 13 illustrates a 1×HE-STF tone in a per-channel PPDU transmissionaccording to an exemplary embodiment of the present invention. Mostparticularly, FIG. 13 shows an example of a HE-STF tone (i.e., 16-tonesampling) having a periodicity of 0.8 μs in 20 MHz/40 MHz/80 MHzbandwidths. Accordingly, in FIG. 13, the HE-STF tones for each bandwidth(or channel) may be positioned at 16 tone intervals.

In FIG. 13, the x-axis represents the frequency domain. The numbers onthe x-axis represent the indexes of a tone, and the arrows representmapping of a value that is not equal to 0 (i.e., a non-zero value) tothe corresponding tone index.

Sub-drawing (a) of FIG. 13 illustrates an example of a 1×HE-STF tone ina 20 MHz PPDU transmission.

Referring to sub-drawing (a), in case a HE-STF sequence (i.e., 1×HE-STFsequence) for a periodicity of 0.8 μs is mapped to tones of a 20 MHzchannel, the 1×HE-STF sequence is mapped to tones having tone indexesthat are divisible by 16 (i.e., multiples of 16), among the tones havingtone indexes ranging from −112 to 112, and, then, 0 may be mapped to theremaining tones. More specifically, in a 20 MHz channel, among the toneshaving tone indexes ranging from −112 to 112, a 1×HE-STF tone may bepositioned at a tone index that is divisible by 16 excluding the DC.Accordingly, a total of 14 1×HE-STF tones having the 1×HE-STF sequencemapped thereto may exist in the 20 MHz channel.

Sub-drawing (b) of FIG. 13 illustrates an example of a 1×HE-STF tone ina 40 MHz PPDU transmission.

Referring to sub-drawing (b), in case a HE-STF sequence (i.e., 1×HE-STFsequence) for a periodicity of 0.8 μs is mapped to tones of a 40 MHzchannel, the 1×HE-STF sequence is mapped to tones having tone indexesthat are divisible by 16 (i.e., multiples of 16), among the tones havingtone indexes ranging from −240 to 240, and, then, 0 may be mapped to theremaining tones. More specifically, in a 40 MHz channel, among the toneshaving tone indexes ranging from −240 to 240, a 1×HE-STF tone may bepositioned at a tone index that is divisible by 16 excluding the DC.Accordingly, a total of 30 1×HE-STF tones having the 1×HE-STF sequencemapped thereto may exist in the 40 MHz channel.

Sub-drawing (c) of FIG. 13 illustrates an example of a 1×HE-STF tone inan 80 MHz PPDU transmission.

Referring to sub-drawing (c), in case a HE-STF sequence (i.e., 1×HE-STFsequence) for a periodicity of 0.8 μs is mapped to tones of a 80 MHzchannel, the 1×HE-STF sequence is mapped to tones having tone indexesthat are divisible by 16 (i.e., multiples of 16), among the tones havingtone indexes ranging from −496 to 496, and, then, 0 may be mapped to theremaining tones. More specifically, in an 80 MHz channel, among thetones having tone indexes ranging from −496 to 496, a 1×HE-STF tone maybe positioned at a tone index that is divisible by 16 excluding the DC.Accordingly, a total of 62 1×HE-STF tones having the 1×HE-STF sequencemapped thereto may exist in the 80 MHz channel.

FIG. 14 illustrates a 2×HE-STF tone in a per-channel PPDU transmissionaccording to an exemplary embodiment of the present invention. Mostparticularly, FIG. 14 shows an example of a HE-STF tone (i.e., 8-tonesampling) having a periodicity of 1.6 μs in 20 MHz/40 MHz/80 MHzbandwidths. Accordingly, in FIG. 14, the HE-STF tones for each bandwidth(or channel) may be positioned at 8 tone intervals.

The 2×HE-STF signal according to FIG. 14 may be applied to the uplink MUPPDU shown in FIG. 12. More specifically, the 2×HE-STF signal shown inFIG. 14 may be included in the PPDU, which is transmitted via uplink inresponse to the above-described trigger frame.

In FIG. 14, the x-axis represents the frequency domain. The numbers onthe x-axis represent the indexes of a tone, and the arrows representmapping of a value that is not equal to 0 (i.e., a non-zero value) tothe corresponding tone index.

Sub-drawing (a) of FIG. 14 is a drawing showing an example of a 2×HE-STFtone in a 20 MHz PPDU transmission.

Referring to sub-drawing (a), in case a HE-STF sequence (i.e., 2×HE-STFsequence) for a periodicity of 1.6 μs is mapped to tones of a 20 MHzchannel, the 2×HE-STF sequence is mapped to tones having tone indexesthat are divisible by 8 (i.e., multiples of 8), among the tones havingtone indexes ranging from −120 to 120, and, then, 0 may be mapped to theremaining tones. More specifically, in a 20 MHz channel, among the toneshaving tone indexes ranging from −120 to 120, a 2×HE-STF tone may bepositioned at a tone index that is divisible by 8 excluding the DC.Accordingly, a total of 30 2×HE-STF tones having the 2× HE-STF sequencemapped thereto may exist in the 20 MHz channel.

Sub-drawing (b) of FIG. 14 illustrates an example of a 2×HE-STF tone ina 40 MHz PPDU transmission.

Referring to sub-drawing (b), in case a HE-STF sequence (i.e., 2×HE-STFsequence) for a periodicity of 1.6 μs is mapped to tones of a 40 MHzchannel, the 2×HE-STF sequence is mapped to tones having tone indexesthat are divisible by 8 (i.e., multiples of 8), among the tones havingtone indexes ranging from −248 to 248, and, then, 0 may be mapped to theremaining tones. More specifically, in a 40 MHz channel, among the toneshaving tone indexes ranging from −248 to 248, a 2×HE-STF tone may bepositioned at a tone index that is divisible by 8 excluding the DC.Herein, however, tones having tone indexes of ±248 correspond to guardtones (left and right guard tones), and such guard tones may beprocessed with nulling (i.e., such guard tones may have a value of 0).Accordingly, a total of 60 2×HE-STF tones having the 2×HE-STF sequencemapped thereto may exist in the 40 MHz channel.

Sub-drawing (c) of FIG. 14 illustrates an example of a 2×HE-STF tone inan 80 MHz PPDU transmission.

Referring to sub-drawing (c), in case a HE-STF sequence (i.e., 2×HE-STFsequence) for a periodicity of 1.6 μs is mapped to tones of an 80 MHzchannel, the 2×HE-STF sequence is mapped to tones having tone indexesthat are divisible by 8 (i.e., multiples of 8), among the tones havingtone indexes ranging from −504 to 504, and, then, 0 may be mapped to theremaining tones. More specifically, in an 80 MHz channel, among thetones having tone indexes ranging from −504 to 504, a 2×HE-STF tone maybe positioned at a tone index that is divisible by 8 excluding the DC.Herein, however, tones having tone indexes of ±504 correspond to guardtones (left and right guard tones), and such guard tones may beprocessed with nulling (i.e., such guard tones may have a value of 0).Accordingly, a total of 124 2×HE-STF tones having the 2×HE-STF sequencemapped thereto may exist in the 80 MHz channel.

Hereinafter, a sequence that can be applied to a 1×HE-STF tone (i.e.,sampling at intervals of 16 tones) and a sequence that can be applied toa 2×HE-STF tone (i.e., sampling at intervals of 8 tones) will beproposed. More specifically, a basic sequence is configured, and a newsequence structure having excellent extendibility by using a nestedstructure in which a conventional sequence is used as a parts of a newsequence is proposed. It is preferable that the M sequence that is usedin the following example corresponds to a sequence having a length of15. It is preferable that the M sequence is configured as a binarysequence so as to decrease the level of complexity when being decoded.

Hereinafter, in a state when a detailed example of an M sequence is notproposed, a basic procedure for generating a sequence in variousbandwidths will be described in detail.

Example (A): Example of a 1×HE-STF Tone

The example of the exemplary embodiment, which will hereinafter bedescribed in detail, may generate an STF sequence supporting diversefrequency bandwidths by using a method of repeating the M sequence,which corresponds to a binary sequence.

FIG. 15 illustrates an example of repeating an M sequence.

It is preferable that the example shown in FIG. 15 is applied to1×HE-STF.

As shown in FIG. 15, when expressed in the form of an equation, the STFsequence for 20 MHz may be expressed as shown in Equation 1.

HE_STF_20 MHz(−112:16:+112)={M}

HE_STF_20 MHz(0)=0  <Equation 1>

The notation of HE_STF(A1:A2:A3)={M}, which is used in Equation 1 andthe other equations shown below is as described below. First of all, thevalue of A1 corresponds to a frequency tone index corresponding to thefirst element of the M sequence, and the value of A3 corresponds to afrequency tone index corresponding to the last element of the Msequence. The value of A2 corresponds to an interval of frequency toneindexes corresponding to each element of the M sequence being positionedbased on the frequency tone interval.

Accordingly, in Equation 1, the first element of the M sequencecorresponds to the frequency band corresponding to index “−112”, thelast element of the M sequence corresponds to the frequency bandcorresponding to index “+112”, and each element of the M sequence ispositioned at 16 frequency tone intervals. Additionally, the value “0”corresponds to a frequency band corresponding to index “0” Morespecifically, Equation 1 has a structure corresponding to sub-drawing(a) of FIG. 13.

As shown in FIG. 15, when expressed in the form of an equation, the STFsequence for 40 MHz may be expressed as shown in Equation 2. Morespecifically, in order to extend the structure of Equation 1 to the 40MHz band, {M, 0, M} may be used.

HE_STF_40 MHz(−240:16:240)={M,0,M}  <Equation 2>

Equation 2 corresponds to a structure, wherein 15 M sequence elementsare positioned within a frequency band range starting from a frequencyband corresponding to index “−240” and up to a frequency bandcorresponding to index “−16” at 16 frequency tone intervals, wherein “0”is positioned for frequency index 0, and wherein 15 M sequence elementsare positioned within a frequency band range starting from a frequencyband corresponding to index “+16” and up to a frequency bandcorresponding to index “+240” at 16 frequency tone intervals “+16”.

As shown in FIG. 15, when expressed in the form of an equation, the STFsequence for 80 MHz may be expressed as shown in Equation 3. Morespecifically, in order to extend the structure of Equation 1 to an 80MHz band, {M, 0, M, 0, M, 0, M} may be used.

HE_STF_80 MHz(−496:16:496)={M,0,M,0,M,0,M}  <Equation 3>

Equation 3 corresponds to a structure, wherein 15 M sequence elementsare positioned within a frequency band range starting from a frequencyband corresponding to index “−496” and up to a frequency bandcorresponding to index “−272” at 16 frequency tone intervals, wherein“0” (or an arbitrary additional value a1) is positioned for a frequencyband corresponding to index “−256”, wherein 15 M sequence elements arepositioned within a frequency band range starting from a frequency bandcorresponding to index “−240” and up to a frequency band correspondingto index “−16” at 16 frequency tone intervals, and wherein “0” ispositioned for frequency index 0. Additionally, Equation 3 alsocorresponds to a structure, wherein 15 M sequence elements arepositioned within a frequency band range starting from a frequency bandcorresponding to index “+16” and up to a frequency band corresponding toindex “+240” at 16 frequency tone intervals, wherein “0” (or anarbitrary additional value a2) is positioned for a frequency bandcorresponding to index “+256”, and wherein M sequence elements arepositioned from “+272” to “+496” at 16 frequency tone intervals.

By applying an additional coefficient to the above-described structuresof Equation 1 to Equation 3, it will be possible to optimize thesequence for PAPR. In case of the related art IEEE 802.11ac system,although it may be possible to extend the predetermined 20 MHz sequencefor the 40 MHz and 80 MHz by using a gamma value, since the gamma valuemay not be applied in the IEEE 802.11ax or HEW system, the PAPR shouldbe considered without considering the gamma value. Additionally, in caseof considering the 1×HE-STF sequence, as shown in Equation 1 to Equation3, the PAPR should be calculated based on the entire band (e.g., theentire band shown in FIG. 4 to FIG. 6), and, in case of considering the2×HE-STF sequence, the PAPR should be calculated while considering eachunit (e.g., individual units 26-RU, 52-RU, 106-RU, and so on, shown inFIG. 4 to FIG. 6).

FIG. 16 is an example specifying the repeated structure of FIG. 15 inmore detail.

As shown in the drawing, coefficients c1 to c7 may be applied, or(1+j)*sqrt(½) may be applied, and additional values, such as a1 and a2,may also be applied.

Based on the content of FIG. 16, an example of the STF sequence that isoptimized for the PAPR is as shown below.

First of all, the M sequence may be determined as shown below inEquation 4.

M={−1,1,−1,1,−1,−1,1,1,−1,−1,1,1,1,1,1}  <Equation 4>

In this case, the STF sequence respective to the 20 MHz and 40 MHz bandsmay be determined in accordance with the equations shown below.

HE_STF_20 MHz(−112:16:112)=M*(1+j)/sqrt(2)

HE_STF_20 MHz(0)=0  <Equation 5>

HE_STF_40 MHz(−240:16:240)={M,0,−M}*(1+j)/sqrt(2)  <Equation 6>

The definition of the variables used in the equations presented above isthe same as those used in Equation 1 to Equation 3.

Meanwhile, the STF sequence corresponding to the 80 MHz band may bedetermined in accordance with any one of the equations shown below.

HE_STF_80 MHz(−496:16:496)={M,1,−M0,−M,1,−M}*(1+j)/sqrt(2)  <Equation 7>

HE_STF_80 MHz(−496:16:496)={M,−1,M0,M,−1,−M}*(1+j)/sqrt(2)  <Equation 8>

The definition of the variables used in the equations presented above isthe same as those used in Equation 1 to Equation 3.

The examples shown in Equation 4 to Equation 8, which are presentedabove, may be modified to other examples, as shown below.

First of all, the M sequence that is basically used may be modified asshown in Equation 9.

M={−1,−1,−1,1,1,1,−1,1,1,1,−1,1,1,−1,1}  <Equation 9>

Equation 9 that is presented above may be applied to all or part ofEquation 5 to Equation 8. For example, it may be possible to use thebasic sequence of Equation 9 based on the structure of Equation 7.

The PAPR for the examples presented in the above-described equations maybe calculated as shown below. As described above, in case of consideringthe 1×HE-STF sequence, the PAPR is calculated based on the entire band(e.g., the entire band shown in FIG. 4 to FIG. 6).

More specifically, the PAPR for the example of applying Equation 4 tothe structure of Equation 5 is equal to 2.33, the PAPR for the exampleof applying Equation 4 to the structure of Equation 6 is equal to 4.40,and the PAPR for the example of applying Equation 4 to the structure ofEquation 7 or Equation 8 is equal to 4.49. Additionally, the PAPR forthe example of applying Equation 9 to the structure of Equation 5 isequal to 1.89, the PAPR for the example of applying Equation 9 to thestructure of Equation 6 is equal to 4.40, and the PAPR for the exampleof applying Equation 9 to the structure of Equation 7 or Equation 8 isequal to 4.53. Although the STF sequences that are presented above showminute differences in the capability of the PAPR, since thecorresponding STF sequences present enhanced PAPR capability as comparedto the related art sequences, it will be preferable to used any one ofthe examples presented above for uplink and/or downlink communication.

Example (B): Example of a 2×HE-STF Tone

It is preferable to apply the example of the exemplary embodiment, whichwill hereinafter be described in detail, to 2×HE-STF.

FIG. 17 illustrates an example of repeating an M sequence.

As shown in FIG. 17, when expressed in the form of an equation, the STFsequence for 20 MHz may be expressed as shown below in the followingEquation.

HE_STF_20 MHz(−120:8:+120)={M,0,M}  <Equation 10>

As shown in FIG. 17, when expressed in the form of an equation, the STFsequence for 40 MHz may be expressed as shown below in the followingEquation.

HE_STF_40 MHz(−248:8:248)={M,0,M,0,M,0,M}  <Equation 11>

As shown in FIG. 17, when expressed in the form of an equation, the STFsequence for 80 MHz may be expressed as shown below in the followingEquation.

HE_STF_80 MHz(−504:8:504)={M,0,M,0,M,0,M,0,M,0,M,0,M,0,M}  <Equation 12>

By applying an additional coefficient to the above-described structuresof Equation 10 to Equation 12, it will be possible to optimize thesequence for PAPR. In case of the related art IEEE 802.11ac system,although it may be possible to extend the predetermined 20 MHz sequencefor the 40 MHz and 80 MHz by using a gamma value, since the gamma valuemay not be applied in the IEEE 802.11ax or HEW system, the PAPR shouldbe considered without considering the gamma value.

FIG. 18 is an example specifying the repeated structure of FIG. 17 inmore detail.

As shown in the drawing, coefficients c1 to c14 may be applied, or(1+j)*sqrt(½) may be applied, and additional values, such as a1 to a8,may also be applied.

Based on the content of FIG. 18, an example of the STF sequence that isoptimized for the PAPR is as shown below.

First of all, the M sequence may be determined as shown below inEquation 13.

M={−1,1,−1,1,−1,−1,1,1,−1,−1,1,1,1,1,1}  <Equation 13>

In this case, the STF sequence respective to the 20 MHz, 40 MHz, and 80MHz bands may be determined in accordance with the equations shownbelow.

HE_STF_20 MHz(−120:8:120)={M,0,−M}*(1+j)/sqrt(2)  <Equation 14>

HE_STF_40 MHz(−248:8:248)={M,1,−M,0,−M,1,M}*(1+j)/sqrt(2)

HE_STF_40 MHz(±248)=0  <Equation 15>

HE_STF_80MHz(−504:8:504)={M,−1,M,−1,M,−1,−M,0,M,1,−M,1,M,1,M}*(1+j)/sqrt(2)

HE_STF_80 MHz(±504)=0  <Equation 16>

The definition of the variables used in the equations presented above isthe same as those used in Equation 1 to Equation 3.

The examples shown in Equation 14 to Equation 16, which are presentedabove, may be modified to other examples, as shown below.

First of all, the M sequence that is basically used may be modified asshown in Equation 17.

M={−1,−1,−1,1,1,1,−1,1,1,1,−1,1,1,−1,1}  <Equation 17>

The 2×HE-STF sequence for the 20 MHz band may be generated by using amethod of applying Equation 17, which is presented above, to Equation14.

Meanwhile, 2×HE-STF sequence for the 40 MHz band may be generated byusing a method of applying Equation 17, which is presented above, to theEquation shown below.

HE_STF_40 MHz(−248:8:248)={M,−1,−M,0,M,−1,M}*(1+j)/sqrt(2)

HE_STF_40 MHz(±248)=0  <Equation 18>

Additionally, 2×HE-STF sequence for the 80 MHz band may be generated byusing a method of applying Equation 17, which is presented above, to theEquation shown below.

HE_STF_80MHz(−504:8:504)={M,−1,M,−1,−M,−1,M,0,−M,1,M,1,−M,1,−M}*(1+j)/sqrt(2)

HE_STF_80 MHz(±504)=0  <Equation 19>

Hereinafter, a 2×HE-STF sequence is proposed to support 80+80/160 MHzband. Specifically, the 2×HE-STF sequence for the 80+80/160 MHz band isproposed by directly duplicating the HE-STF sequence for the 80 MHz bandproposed in the example of 2×HE-STF tone (example (B)).

However, when the HE-STF sequence for the 80+80/160 MHz band is used bydirectly duplicating the HE-STF sequence for the 80 MHz band, the PAPRincreases due to the characteristics of the repeated sequence (802.11acsystem).

Therefore, in order to lower the PAPR, the present specificationproposes a method of configuring a HE-STF sequence for the 80+80/160 MHzband in which the sequence in the second 80 MHz band is formed byapplying phase rotation to a specific band for the sequence in the first80 MHz band.

Specifically, an example of the 2×HE-STF sequence optimized with respectto the PAPR is as follows.

First, the basically used M sequence may be determined as shown inEquation 20.

M={−1,−1,−1,1,1,1,−1,1,1,1,−1,1,1,−1,1}  <Equation 20>

In this case, the 2×HE-STF sequence for the 80 MHz band may bedetermined as follows.

HE_STF_80MHz(−504:8:504)={M,−1,M,−1,−M,−1,M,0,−M,1,M,1,−M,1,−M}*(1+j)/sqrt(2)

HE_STF_80 MHz(±504)=0  <Equation 21>

In this case, the 2×HE-STF sequence for the 80+80/160 MHz band may begenerated by duplicating the sequence of the Equation 21 directly(Option 1) or may be generated by applying a phase rotation to thesequence of the Equation 21 (Option 2 through 18). In the case ofapplying the phase rotation to the sequence of the Equation 21, the2×HE-STF sequence for the 80+80/160 MHz band may be generated byapplying a phase rotation for each 40 MHz subband (Option 2 to 4), ormay be generated by applying a phase rotation for each 20 MHz subband(Option 5 to 18).

That is, the 80+80/160 MHz band may be composed of a primary 80 MHz anda secondary 80 MHz. In options to be described later, it may begenerated by applying a phase rotation by the 40 MHz subband or the 20MHz subband to the secondary 80 MHz. In particular, the option 2 to bedescribed later may apply the phase rotation −1 to the first 40 MHz ofthe secondary 80 MHz.

For the convenience of explanation, it is assumed that the Equation 21(HE_STF_80 MHz (−504:8:504)) used in the following Option 1 to 18 isrepresented in HES.

-   -   Option 1: dup [HES HES]    -   Option 2: [HES HES1]

HES1={−[M,−1,M,−1,−M,−1,M],0,−M,1,M,1,−M,1,−M}*(1+j)*sqrt(½)

HES1_(−504,504)(±504)=0

-   -   Option 3: [HES HES2]

HES2={M,−1,M,−1,−M,−1,M,0,−[−M,1,M,1,−M,1,−M]}*(1+j)*sqrt(½)

HES2_(−504,504)(±504)=0

-   -   Option 4: [HES HES3]

HES3={−[M,−1,M,−1,−M,−1,M],0,−[−M,1,M,1,−M,1,−M]}*(1+j)*sqrt(½)

HES3_(−504,504)(±504)=0

-   -   Option 5: [HES HES4]

HES4={−[M,−1,M],[−1,−M,−1,M],0,[−M,1,M],[1,−M,1,−M]}*(1+j)*sqrt(½)

HES4_(−504,504)(±504)=0

-   -   Option 6: [HES HES5]

HES5={−[M,−1,M],−[−1,−M,−1,M],0,[−M,1,M],[1,−M,1,−M]}*(1+j)*sqrt(½)

HES5_(−504,504)(±504)=0

-   -   Option 7: [HES HES6]

HES6={−[M,−1,M],[−1,−M,−1,M],0,−[−M,1,M],[1,−M,1,−M]}*(1+j)*sqrt(½)

HES6_(−504,504)(±504)=0

-   -   Option 8: [HES HES7]

HES7={−[M,−1,M],[−1,−M,−1,M],0,[−M,1,M],−[−1,−M,1,−M]}*(1+j)*sqrt(½)

HES7_(−504,504)(±504)=0

-   -   Option 9: [HES HES8]

HES8={−[M,−1,M],−[−1,−M,−1,M],0,−[−M,1,M],[1,−M,1,−M]}*(1+j)*sqrt(½)

HES8_(−504,504)(±504)=0

-   -   Option 10: [HES HES9]

HES9={−[M,−1,M],−[−1,−M,−1,M],0,[−M,1,M],−[1,−M,1,−M]}*(1+j)*sqrt(½)

HES9_(−504,504)(±504)=0

-   -   Option 11: [HES HES10]

HES10={−[M,−1,M],[−1,−M,−1,M],0,−[−M,1,M],−[1,−M,1,−M]}*(1+j)*sqrt(½)

HES10_(−504,504)(±504)=0

-   -   Option 12: [HES HES11]

HES11={[M,−1,M],−[−1,−M,−1,M],0,[−M,1,M],[1,−M,1,−M]}*(1+j)*sqrt(½)

HES11_(−504,504)(±504)=0

-   -   Option 13: [HES HES12]

HES12={[M,−1,M],−[−1,−M,−1,M],0,−[−M,1,M],[1,−M,1,−M]}*(1+j)*sqrt(½)

HES12_(−504,504)(±504)=0

-   -   Option 14: [HES HES13]

HES13={[M,−1,M],−[−1,−M,−1,M],0,[−M,1,M],−[1,−M,1,−M]}*(1+j)*sqrt(½)

HES13_(−504,504)(±504)=0

-   -   Option 15: [HES HES14]

HES14={[M,−1,M],−[−1,−M,−1,M],0,−[−M,1,M],−[1,−M,1,−M]}*(1+j)*sqrt(½)

HES14_(−504,504)(±504)=0

-   -   Option 16: [HES HES15]

HES15={[M,−1,M],[−1,−M,−1,M],0,−[−M,1,M],[1,−M,1,−M]}*(1+j)*sqrt(½)

HES15_(−504,504)(±504)=0

-   -   Option 17: [HES HES16]

HES16={[M,−1,M],[−1,−M,−1,M],0,−[−M,1,M],−[1,−M,1,−M]}*(1+j)*sqrt(½)

HES16_(−504,504)(±504)=0

-   -   Option 18: [HES HES17]

HES17={[M,−1,M],[−1,−M,−1,M],0,[−M,1,M],−[1,−M,1,−M]}*(1+j)*sqrt(½)

HES17_(−504,504)(±504)=0

According to the above example, the PAPR may be calculated and shown inTables 1 to 18 and FIGS. 19 to 33 for the 2×HE-STF sequence for the80+80/160 MHz band.

Herein, the PAPR should be calculated considering both RU units (e.g.,26-RU, 52-RU, and 106-RU, etc. shown in FIGS. 4 to 6), and the entireband (e.g., the entire band shown in FIGS. 4 to 6) for the 2×HE-STFsequence for the 80+80/160 MHz band. This is because the 2×HE-STFsequence is included in trigger-based PPDUs in which a trigger frame istransmitted with specifying the RU. That is, the transmitting apparatustransmits the PPDU to the receiving apparatus through each RU unit orthe entire band.

Also, the channel spacing may correspond to the spacing between thecenter frequency of the first 80 MHz and that of the second 80 MHz.Therefore, if the channel spacing is 80 MHz, it may be seen that thefirst 80 MHz and the second 80 MHz are almost adjacent to each other.

FIG. 19 is a diagram illustrating the above-mentioned example of PAPRexpressed in RU units used in the 80+80/160 MHz band.

The entire band illustrated in FIG. 19 is composed of a left hand sideof 80 MHz and a right hand side of another 80 MHz. That is, each blockillustrated in the left hand side and the right hand side in FIG. 19represents 26-RU, 52-RU, 106-RU, 242-RU, and 484-RU illustrated in FIG.6. For example, a first block 1910 represents the leftmost 26-RUillustrated in FIG. 6, a second block 1920 represents the 52-RU, a thirdblock 1930 represents the 106-RU, a fourth block 1940 represents the242-RU, and a fifth block 1950 represents the 484-RU.

An example of the above-mentioned Equations 17 to 19 may be representedby an example (B-1). In this case, the numerical value indicated in eachblock represents the PAPR for the example (B-1).

Referring to FIG. 19, when the 2×HE-STF sequence for the 80+80/160 MHzband is Option 1 to 4, PAPRs of the 2×HE-STF sequences are equal to eachother for the respective RUs. However, though the Option 1 to 4 areselected, PAPRs have different values for the 26-RU (i.e., center 26tone RU) located in the DC band, the 996-RU (996 tone RU), and the 160MHz. For the transmission frequency of the 2×HE-STF sequence is 160 MHz,it means that the channel interval of the center frequency is 80 MHz.The PAPRs having different values may be represented as shown in Table 1below.

TABLE 1 Center 26 tone RU 996 tone RU 160 MHz Option 1 1.9381 5.77067.8730 Option 2 3.0103 6.9701 6.3028 Option 3 3.0103 6.9701 6.6530Option 4 1.9381 5.7706 8.7809

Further, when the 2×HE-STF sequence is Options 1 to 4 for the 80+80 160MHz band, the PAPR for the entire band may be expressed as shown inTable 2 below.

TABLE 2 Channel Interval [MHz] Option 1 Option 2 Option 3 Option 4 80(adjacent) 7.8730 6.3028 6.6530 8.7809 100 8.4075 5.4362 6.9868 8.0933120 7.8883 6.1762 5.9999 7.7017 140 8.0933 6.9868 6.5733 8.2208 1608.7809 4.4834 4.4834 8.5760 180 8.0933 6.5733 6.9868 8.2208 200 7.88835.9999 6.1762 7.7017 220 8.4075 6.9868 5.4362 8.0933 240 7.8730 6.65306.3028 8.7809 >240 9.0300 6.9868 6.9868 15.0512

FIG. 20 is a diagram illustrating the above-mentioned example of PAPRexpressed in RU units used in the 80+80/160 MHz band.

The entire band illustrated in FIG. 20 is composed of a left hand sideof 80 MHz and a right hand side of another 80 MHz. That is, each blockillustrated in the left hand side and the right hand side in FIG. 20represents 26-RU, 52-RU, 106-RU, 242-RU, and 484-RU illustrated in FIG.6.

Referring to FIG. 20, when the 2×HE-STF sequence is Option 5 for the80+80/160 MHz band, the PAPR is 1.94 for the 26-RU (i.e., the center 26tone RU) located in the DC band, and the PAPR is 6.0183 for the 996-RU(the 996 tone RU).

Further, when the 2×HE-STF sequence is Option 5 for the 80+80/160 MHzband, the PAPR for the entire band may be expressed as shown in Table 3below.

TABLE 3 Channel Interval [MHz] Option 5 80 (adjacent) 7.8167 100 7.8167120 7.8167 140 7.8167 160 8.0876 180 7.8167 200 7.8167 220 7.8167 2407.8167 >240 8.9737

FIG. 21 is a diagram illustrating the above-mentioned example of PAPRexpressed in RU units used in the 80+80/160 MHz band.

The entire band illustrated in FIG. 21 is composed of a left hand sideof 80 MHz and a right hand side of another 80 MHz. That is, each blockillustrated in the left hand side and the right hand side in FIG. 21represents 26-RU, 52-RU, 106-RU, 242-RU, and 484-RU illustrated in FIG.6.

Referring to FIG. 21, when the 2×HE-STF sequence is Option 6 for the80+80/160 MHz band, the PAPR is 3.01 for the 26-RU (i.e., the center 26tone RU) located in the DC band, and the PAPR is 6.9701 for the 996-RU(the 996 tone RU).

Further, when the 2×HE-STF sequence is Option 6 (Option 2) for the80+80/160 MHz band, the PAPR for the entire band may be expressed asshown in Table 4 below.

TABLE 4 Channel Interval [MHz] Option 6 80 (adjacent) 6.3028 100 5.4362120 6.1762 140 6.9868 160 4.4834 180 6.5733 200 5.9999 220 6.9868 2406.6530 >240 6.9868

FIG. 22 is a diagram illustrating the above-mentioned example of PAPRexpressed in RU units used in the 80+80/160 MHz band.

The entire band illustrated in FIG. 22 is composed of a left hand sideof 80 MHz and a right hand side of another 80 MHz. That is, each blockillustrated in the left hand side and the right hand side in FIG. 22represents 26-RU, 52-RU, 106-RU, 242-RU, and 484-RU illustrated in FIG.6.

Referring to FIG. 22, when the 2×HE-STF sequence is Option 7 for the80+80/160 MHz band, the PAPR is 3.01 for the 26-RU (i.e., the center 26tone RU) located in the DC band, and the PAPR is 7.4272 for the 996-RU(the 996 tone RU).

Further, when the 2×HE-STF sequence is Option 7 for the 80+80/160 MHzband, the PAPR for the entire band may be expressed as shown in Table 5below.

TABLE 5 Channel Interval [MHz] Option 7 80 (adjacent) 5.8722 100 7.0865120 7.7718 140 6.0809 160 5.8166 180 6.8377 200 6.4259 220 7.4567 2407.2077 >240   7.8070

FIG. 23 is a diagram illustrating the above-mentioned example of PAPRexpressed in RU units used in the 80+80/160 MHz band.

The entire band illustrated in FIG. 23 is composed of a left hand sideof 80 MHz and a right hand side of another 80 MHz. That is, each blockillustrated in the left hand side and the right hand side in FIG. 23represents 26-RU, 52-RU, 106-RU, 242-RU, and 484-RU illustrated in FIG.6.

Referring to FIG. 23, when the 2×HE-STF sequence is Option 8 for the80+80/160 MHz band, the PAPR is 1.9381 for the 26-RU (i.e., the center26 tone RU) located in the DC band, and the PAPR is 6.9785 for the996-RU (the 996 tone RU).

Further, when the 2×HE-STF sequence is Option 8 for the 80+80/160 MHzband, the PAPR for the entire band may be expressed as shown in Table 6below.

TABLE 6 Channel Interval [MHz] Option 8 80 (adjacent) 7.7141 100 7.7141120 7.7141 140 7.7141 160 7.7141 180 7.7141 200 7.7141 220 7.7141 2407.7141 >240   7.7493

FIG. 24 is a diagram illustrating the above-mentioned example of PAPRexpressed in RU units used in the 80+80/160 MHz band.

The entire band illustrated in FIG. 24 is composed of a left hand sideof 80 MHz and a right hand side of another 80 MHz. That is, each blockillustrated in the left hand side and the right hand side in FIG. 24represents 26-RU, 52-RU, 106-RU, 242-RU, and 484-RU illustrated in FIG.6.

Referring to FIG. 24, when the 2×HE-STF sequence is Option 9 for the80+80/160 MHz band, the PAPR is 1.9381 for the 26-RU (i.e., the center26 tone RU) located in the DC band, and the PAPR is 5.2260 for the996-RU (the 996 tone RU).

Further, when the 2×HE-STF sequence is Option 9 for the 80+80/160 MHzband, the PAPR for the entire band may be expressed as shown in Table 7below.

TABLE 7 Channel Interval [MHz] Option 9 80 (adjacent) 8.1297 100 7.4907120 7.3313 140 7.8546 160 8.0381 180 7.8851 200 7.3834 220 7.4008 2408.1297 >240   8.6477

FIG. 25 is a diagram illustrating the above-mentioned example of PAPRexpressed in RU units used in the 80+80/160 MHz band.

The entire band illustrated in FIG. 25 is composed of a left hand sideof 80 MHz and a right hand side of another 80 MHz. That is, each blockillustrated in the left hand side and the right hand side in FIG. 25represents 26-RU, 52-RU, 106-RU, 242-RU, and 484-RU illustrated in FIG.6.

Referring to FIG. 25, when the 2×HE-STF sequence is Option 10 for the80+80/160 MHz band, the PAPR is 3.0103 for the 26-RU (i.e., the center26 tone RU) located in the DC band, and the PAPR is 5.6104 for the996-RU (the 996 tone RU).

Further, when the 2×HE-STF sequence is Option 10 for the 80+80/160 MHzband, the PAPR for the entire band may be expressed as shown in Table 8below.

TABLE 8 Channel Interval [MHz] Option 10 80 (adjacent) 6.9296 100 6.0243120 7.0812 140 6.3355 160 7.1749 180 6.3813 200 4.8705 220 6.5934 2406.9296 >240   7.1812

FIG. 26 is a diagram illustrating the above-mentioned example of PAPRexpressed in RU units used in the 80+80/160 MHz band.

The entire band illustrated in FIG. 26 is composed of a left hand sideof 80 MHz and a right hand side of another 80 MHz. That is, each blockillustrated in the left hand side and the right hand side in FIG. 26represents 26-RU, 52-RU, 106-RU, 242-RU, and 484-RU illustrated in FIG.6.

Referring to FIG. 26, when the 2×HE-STF sequence is Option 11 for the80+80/160 MHz band, the PAPR is 3.0103 for the 26-RU (i.e., the center26 tone RU) located in the DC band, and the PAPR is 5.9261 for the996-RU (the 996 tone RU).

Further, when the 2×HE-STF sequence is Option 11 for the 80+80/160 MHzband, the PAPR for the entire band may be expressed as shown in Table 9below.

TABLE 9 Channel Interval [MHz] Option 11 80 (adjacent) 7.1123 100 6.7352120 5.0630 140 6.7766 160 6.8017 180 6.4070 200 7.5496 220 6.4070 2407.1123 >240   7.5640

FIG. 27 is a diagram illustrating the above-mentioned example of PAPRexpressed in RU units used in the 80+80/160 MHz band.

The entire band illustrated in FIG. 27 is composed of a left hand sideof 80 MHz and a right hand side of another 80 MHz. That is, each blockillustrated in the left hand side and the right hand side in FIG. 27represents 26-RU, 52-RU, 106-RU, 242-RU, and 484-RU illustrated in FIG.6.

Referring to FIG. 27, when the 2×HE-STF sequence is Option 12 for the80+80/160 MHz band, the PAPR is 3.0103 for the 26-RU (i.e., the center26 tone RU) located in the DC band, and the PAPR is 5.9261 for the996-RU (the 996 tone RU).

Further, when the 2×HE-STF sequence is Option 12 for the 80+80/160 MHzband, the PAPR for the entire band may be expressed as shown in Table 10below.

TABLE 10 Channel Interval [MHz] Option 12 80 (adjacent) 6.9377 1006.5898 120 6.7563 140 6.1628 160 7.1123 180 7.3502 200 6.8440 220 7.4155240 6.4070 >240   7.7130

FIG. 28 is a diagram illustrating the above-mentioned example of PAPRexpressed in RU units used in the 80+80/160 MHz band.

The entire band illustrated in FIG. 28 is composed of a left hand sideof 80 MHz and a right hand side of another 80 MHz. That is, each blockillustrated in the left hand side and the right hand side in FIG. 28represents 26-RU, 52-RU, 106-RU, 242-RU, and 484-RU illustrated in FIG.6.

Referring to FIG. 28, when the 2×HE-STF sequence is Option 13 for the80+80/160 MHz band, the PAPR is 1.9381 for the 26-RU (i.e., the center26 tone RU) located in the DC band, and the PAPR is 6.9785 for the996-RU (the 996 tone RU).

Further, when the 2×HE-STF sequence is Option 13 for the 80+80/160 MHzband, the PAPR for the entire band may be expressed as shown in Table 11below.

TABLE 11 Channel Interval [MHz] Option 13 80 (adjacent) 6.9117 1007.3364 120 7.4060 140 7.3844 160 7.6932 180 7.3665 200 7.1338 220 7.6319240 6.9117 >240   8.5235

FIG. 29 is a diagram illustrating the above-mentioned example of PAPRexpressed in RU units used in the 80+80/160 MHz band.

The entire band illustrated in FIG. 29 is composed of a left hand sideof 80 MHz and a right hand side of another 80 MHz. That is, each blockillustrated in the left hand side and the right hand side in FIG. 29represents 26-RU, 52-RU, 106-RU, 242-RU, and 484-RU illustrated in FIG.6.

Referring to FIG. 29, when the 2×HE-STF sequence is Option 14 for the80+80/160 MHz band, the PAPR is 3.0103 for the 26-RU (i.e., the center26 tone RU) located in the DC band, and the PAPR is 7.4272 for the996-RU (the 996 tone RU).

Further, when the 2×HE-STF sequence is Option 14 for the 80+80/160 MHzband, the PAPR for the entire band may be expressed as shown in Table 12below.

TABLE 12 Channel Interval [MHz] Option 14 80 (adjacent) 7.2077 1006.8377 120 6.6200 140 7.4567 160 5.5439 180 5.7715 200 7.7718 220 6.9932240 5.8722 >240   7.7718

FIG. 30 is a diagram illustrating the above-mentioned example of PAPRexpressed in RU units used in the 80+80/160 MHz band.

The entire band illustrated in FIG. 30 is composed of a left hand sideof 80 MHz and a right hand side of another 80 MHz. That is, each blockillustrated in the left hand side and the right hand side in FIG. 30represents 26-RU, 52-RU, 106-RU, 242-RU, and 484-RU illustrated in FIG.6.

Referring to FIG. 30, when the 2×HE-STF sequence is Option 15 for the80+80/160 MHz band, the PAPR is 1.9381 for the 26-RU (i.e., the center26 tone RU) located in the DC band, and the PAPR is 6.0183 for the996-RU (the 996 tone RU).

Further, when the 2×HE-STF sequence is Option 15 for the 80+80/160 MHzband, the PAPR for the entire band may be expressed as shown in Table 13below.

TABLE 13 Channel Interval [MHz] Option 15 80 (adjacent) 8.0876 1007.5502 120 7.3604 140 7.9534 160 8.1897 180 8.0887 200 7.6421 220 7.2558240 8.0876 >240   8.4128

FIG. 31 is a diagram illustrating the above-mentioned example of PAPRexpressed in RU units used in the 80+80/160 MHz band.

The entire band illustrated in FIG. 31 is composed of a left hand sideof 80 MHz and a right hand side of another 80 MHz. That is, each blockillustrated in the left hand side and the right hand side in FIG. 31represents 26-RU, 52-RU, 106-RU, 242-RU, and 484-RU illustrated in FIG.6.

Referring to FIG. 31, when the 2×HE-STF sequence is Option 16 for the80+80/160 MHz band, the PAPR is 3.0103 for the 26-RU (i.e., the center26 tone RU) located in the DC band, and the PAPR is 5.6104 for the996-RU (the 996 tone RU).

Further, when the 2×HE-STF sequence is Option 16 for the 80+80/160 MHzband, the PAPR for the entire band may be expressed as shown in Table 14below.

TABLE 14 Channel Interval [MHz] Option 16 80 (adjacent) 6.0243 1007.1997 120 6.5451 140 6.8937 160 6.9296 180 5.9075 200 6.9449 220 6.8744240 6.4362 >240   7.5713

FIG. 32 is a diagram illustrating the above-mentioned example of PAPRexpressed in RU units used in the 80+80/160 MHz band.

The entire band illustrated in FIG. 32 is composed of a left hand sideof 80 MHz and a right hand side of another 80 MHz. That is, each blockillustrated in the left hand side and the right hand side in FIG. 32represents 26-RU, 52-RU, 106-RU, 242-RU, and 484-RU illustrated in FIG.6.

Referring to FIG. 32, when the 2×HE-STF sequence is Option 17 for the80+80/160 MHz band, the PAPR is 3.0103 for the 26-RU (i.e., the center26 tone RU) located in the DC band, and the PAPR is 6.9701 for the996-RU (the 996 tone RU).

Further, when the 2×HE-STF sequence is Option 17 for the 80+80/160 MHzband, the PAPR for the entire band may be expressed as shown in Table 15below.

TABLE 15 Channel Interval [MHz] Option 17 80 (adjacent) 6.6530 1006.9868 120 5.9999 140 6.5733 160 4.4834 180 6.9868 200 6.1762 220 5.4362240 6.3028 >240   6.9868

FIG. 33 is a diagram illustrating the above-mentioned example of PAPRexpressed in RU units used in the 80+80/160 MHz band.

The entire band illustrated in FIG. 33 is composed of a left hand sideof 80 MHz and a right hand side of another 80 MHz. That is, each blockillustrated in the left hand side and the right hand side in FIG. 33represents 26-RU, 52-RU, 106-RU, 242-RU, and 484-RU illustrated in FIG.6.

Referring to FIG. 33, when the 2×HE-STF sequence is Option 18 for the80+80/160 MHz band, the PAPR is 1.9381 for the 26-RU (i.e., the center26 tone RU) located in the DC band, and the PAPR is 5.2260 for the996-RU (the 996 tone RU).

Further, when the 2×HE-STF sequence is Option 18 for the 80+80/160 MHzband, the PAPR for the entire band may be expressed as shown in Table 16below.

TABLE 16 Channel Interval [MHz] Option 18 80 (adjacent) 7.6361 1007.6361 120 7.6361 140 7.6361 160 8.1297 180 7.6361 200 7.6361 220 7.6361240 7.6361 >240   8.7931

As a result, the maximum PAPR of the 2×HE-STF sequence on the entireOption (Option 1 to 18) for the 80+80/160 MHz band may be expressed asshown in Table 17 and Table 18 below. Table 17 shows the maximum PAPR ofthe OFDMA RUs and the number of RUs (indicated by parentheses) havingthe PAPR value greater than 6. Table 18 shows the maximum PAPR of theentire band.

TABLE 17 Option Option 1 Option 2 Option 3 Option 4 Option 5 6(2)5.77(0) 6.97(1) 6.97(1) 5.77(0) 6.57(2) 6.97(1) Option 7 Option 8 Option9 Option 10 Option 11 Option 12 7.43(4) 6.98(4) 6.02(2) 6.02(2) 6.57(1)6.57(1) Option Option 13 Option 14 Option 15 Option 16 17(3) Option 186.98(4) 7.43(4) 6.57(2) 6.02(2) 6.97(1) 6.02(2)

TABLE 18 Option Option 1 Option 2 Option 3 Option 4 Option 5 6(2) 9.036.99 6.99 15.05  8.97 6.99 Option 7 Option 8 Option 9 Option 10 Option11 Option 12 7.81 7.75 8.65 7.18 7.56 7.71 Option Option 13 Option 14Option 15 Option 16 17(3) Option 18 8.52 7.77 8.41 7.57 6.99 8.79

Referring to Table 17 and Table 18, it may be seen that the Option 1 isduplicated, and thus the performance for each OFDMA RU is good but theperformance for the entire band is not good. In addition, the Option 4is duplicated with its sign changed, and thus it shows similarperformances as the Option 1.

Therefore, considering the performance for each OFDMA RU and theperformance for the entire bands with respect to PAPR, using the Option2 and Option 3 as the 2×HE-STF sequence will give the best performance.The number of RUs having the PAPR value greater than 6 is 1 and it isnot so large, and the maximum PAPR of the entire band is 6.99, which isnot large when compared with other options. As the second best, it isalso desirable to use the Option 11 and Option 12 as the 2×HE-STFsequence for the 80+80/160 MHz band. It is allowed to use the Option 10and Option 16, but the performance is not good as the maximum PAPR incase of the 26-RU is calculated to be 6.02.

Further, the present specification proposes the HE-STF sequence forsupporting the 80+80/160 MHz band in UL OFDMA transmission.Specifically, it is proposed that the HE-STF sequence of a secondarychannel is replaced with the HE-STF sequence of a primary channel inorder to lower the PAPR. Here, as the performance is considered for eachOFDMA RU, the HE-STF sequence may be the 2×HE-STF sequence.

The HE-STF sequence may be set illustratively as follows for the80+80/160 MHz band to which the above technique may be applied.

-   -   The 2×HE-STF sequence for the 80+80/160 MHz band=[HES HES1]

HES={M,−1,M,−1,−M,−1,M,0,−M,1,M,1,−M,1,−M}*(1+j)*sqrt(½)

HES _(−504,504)(±504)=0

HES1={−[M,−1,M,−1,−M,−1,M],0,−M,1,M,1,−M,1,−M}*(1+j)*sqrt(½)

HES1_(−504,504)(±504)=0

An example of PAPR for the above 2×HE-STF sequence is illustrated inFIG. 19 in units of RUs used in the 80+80/160 MHz band. In this case,the PAPRs of the primary and secondary channels are the same except forthe 26-RU (i.e., center 26 tone RU) and the 996-RU (996 tone RU).

The PAPR of the center 26-tone RU and 996-tone RU for the primary andsecondary channels is shown in Table 19 below. The center 26-tone RU and996-tone of the primary channel may be corresponded to the center26-tone RU and the 996-tone for the first 80 MHz band of the 80+80/160MHz band. The center 26-tone RU and 996 tone of the secondary channelmay be corresponded to the center 26-tone RU and the 996-tone for thesecond 80 MHz band of the 80+80/160 MHz band.

TABLE 19 Center 26 tone RU 996 tone RU Primary 1.9381 5.7706 Secondary3.0103 6.9701

Referring to the Table 19, a transmitting apparatus transmitting ULOFDMA using the center 26-tone RU and the 996-tone RU of the secondarychannel will have a somewhat higher PAPR. Therefore, when the UL OFDMAis transmitted using the center 26-tone RU and the 996-tone RU of thesecondary channel, the HE-STF sequence may be transmitted using theHE-STF sequence of the primary channel other than the HE-STF sequence ofthe secondary channel is. If the HE-STF sequence of the primary channelis used, it may obtain much better performance with respect to the PAPRthan using the HE-STF sequence of the secondary channel.

The above process may be expressed by the following equation. First, thesequence index of the center 26-tone RU of the primary 80 MHz and thecenter 26-tone RU of the secondary 80 MHz is (−16:−4, 4:16). Thesequence index of the 996-tone RU for the primary 80 MHz and the996-tone RU for the secondary 80 MHz are (−500:−3, 3:500). Therefore,the HE-STF sequence for the 80+80/160 MHz band may be expressed inEquation below according to the above-described method. Here, the HES1may correspond to the HE-STF sequence of the secondary 80 MHz. The HESmay support the HE-STF sequence of primary 80 MHz.

The HE-STF sequence for the 80+80/160 MHz band: [HES HES1]

HES1(−16:16)=HES(−16:16)

HES1(−500:500)=HES(−500:500)  <Equation 22>

FIG. 34 is a flowchart which may apply the above embodiment.

An example of FIG. 34 is applicable to various transmitting apparatus.

In step S3410, the transmitting apparatus determines whether to transmitthe 1×HE-STF signal or the 2×HE STF signal. For example, in response tothe trigger frame shown in FIG. 9, when transmitting the uplink PPDUshown in FIG. 12, the 2×HE STF signal may be transmitted; otherwise, the1×HE STF signal may be transmitted.

If the 2×HE-STF is to be transmitted, the 2×HE-STF signal may begenerated according to step S3420. If the 1×HE-STF is to be transmitted,the 1×HE-STF signal may be generated according to step S3430. Here, itis only assumed the case that the 2×HE-STF is to be transmitted (thatis, the case of transmitting the HE PPDU corresponding to the triggerframe shown in FIG. 12).

For example, when generating a short training field (STF) signalcorresponding to a first frequency band (for example, 80+80 MHz or 160MHz band), the STF signal corresponding to the first frequency band maybe generated based on a sequence in which a preset M sequence isrepeated. In this case, the repeated sequence may be defined as {M, −1,M, −1, −M, −1, M, 0, −M, 1, M, 1, −M, 1, −M, 0, −M, 1, −M, 1, M, 1, −M,0, −M, 1, M, 1, −M, 1, −M}*(1+j)/sqrt(2). The M sequence may be equal toM={−1, −1, −1, 1, 1, 1, −1, 1, 1, 1, −1, 1, 1, −1, 1}. The sequence of{M, −1, M, −1, −M, −1, M, 0, −M, 1, M, 1, −M, 1, −M, 0, −M, 1, −M, 1, M,1, −M, 0, −M, 1, M, 1, −M, 1, −M}*(1+j)/sqrt(2) may be arranged in a8-tone interval from the lowest tone with tone index −1016 to thehighest tone with tone index +1016. Further, in the sequence of {M, −1,M, −1, −M, −1, M, 0, −M, 1, M, 1, −M, 1, −M, 0, −M, 1, −M, 1, M, 1, −M,0, −M, 1, M, 1, −M, 1, −M}*(1+j)/sqrt(2), elements corresponding to toneindex −8, 8, −1016 and 1016 may be nulled. Further, when the STF signalcorresponding to the second frequency band is generated, the sequence of{M, −1, M, −1, −M, −1, M, 0, −M, 1, M, 1, −M, 1, −M}*(1+j)/sqrt(2),etc., may be used.

Further, the STF signal corresponding to the first frequency band may begenerated based on a sequence for a primary channel and a sequence for asecondary channel. The sequence for the secondary channel may bereplaced with the sequence for the primary channel. This is to lower theoverall PAPR considering the primary channel and the secondary channelwhen transmitting the HE-STF.

Firstly, the primary channel and the secondary channel may support aplurality of frequency resource units (RUs). Specifically, the PAPRvalue generated when HE-STF is transmitted using the center 26-RU andthe 996-RU of the secondary channel is greater than when HE-STF istransmitted using the center 26-RU and the 996-RU of the primarychannel. Thus, in order to reduce the overall PAPR, the sequencecorresponding to the center 26-RU and the 996-RU of the secondarychannel may be replaced with the sequence corresponding to the center26-RU and the 996-RU of the primary channel.

If the 2×HE-STF is to be transmitted, in the step S3420, at least anyone of the 2×HE-STF signal presented in the above example (B) may beused.

If the 1×HE-STF is transmitted, the 1×HE-STF signal may be generatedaccording to the step S3430. In this case, at least any one of the1×HE-STF signals presented in the above example (A) may be used.

In step S3440, the generated HE-STF signal is transmitted to thereceiving apparatus.

FIG. 35 is a block view showing a wireless device to which the exemplaryembodiment of the present invention can be applied.

Referring to FIG. 35, as a station (STA) that can implement theabove-described exemplary embodiment, the wireless device may correspondto an AP or a non-AP station (non-AP STA). The wireless device maycorrespond to the above-described user or may correspond to atransmitting device transmitting a signal to the user.

The AP 3500 includes a processor 3510, a memory 3520, and a radiofrequency unit (RF unit) 3530.

The RF unit 3530 is connected to the processor 3510, thereby beingcapable of transmitting and/or receiving radio signals.

The processor 3510 implements the functions, processes, and/or methodsproposed in this specification. For example, the processor 3510 may berealized to perform the operations according to the above-describedexemplary embodiments of the present invention. More specifically, theprocessor 3510 may perform the operations that can be performed by theAP, among the operations that are disclosed in the exemplary embodimentsof FIG. 1 to FIG. 34.

The non-AP STA 3550 includes a processor 3560, a memory 3570, and aradio frequency (RF) unit 3580.

The RF unit 3580 is connected to the processor 3560, thereby beingcapable of transmitting and/or receiving radio signals.

The processor 3560 may implement the functions, processes, and/ormethods proposed in the exemplary embodiment of the present invention.For example, the processor 3560 may be realized to perform the non-APSTA operations according to the above-described exemplary embodiments ofthe present invention. The processor may perform the operations of thenon-AP STA, which are disclosed in the exemplary embodiments of FIG. 1to FIG. 34.

The processor 3510 and 3560 may include an application-specificintegrated circuit (ASIC), another chip set, a logical circuit, a dataprocessing device, and/or a converter converting a baseband signal and aradio signal to and from one another. The memory 3520 and 3570 mayinclude a read-only memory (ROM), a random access memory (RAM), a flashmemory, a memory card, a storage medium, and/or another storage device.The RF unit 3530 and 3580 may include one or more antennas transmittingand/or receiving radio signals.

When the exemplary embodiment is implemented as software, theabove-described method may be implemented as a module (process,function, and so on) performing the above-described functions. Themodule may be stored in the memory 3520 and 3570 and may be executed bythe processor 3510 and 3560. The memory 3520 and 3570 may be locatedinside or outside of the processor 3510 and 3560 and may be connected tothe processor 3510 and 3560 through a diversity of well-known means.

1. A method of transmitting a training signal in a wireless LAN systemsupporting a plurality of frequency bands, the method comprising:generating, by a transmitting apparatus, a short training field (STF)signal corresponding to a first frequency band of the plurality offrequency bands; and transmitting, by the transmitting apparatus, a PPDU(physical protocol data unit) including the STF signal to a receivingapparatus, and wherein the STF signal corresponding to the firstfrequency band is generated based on a sequence in which a preset Msequence is repeated, and wherein the repeated sequence is defined as{M, −1, M, −1, −M, −1, M, 0, −M, 1, M, 1, −M, 1, −M, 0, −M, 1, −M, 1, M,1, −M, 0, −M, 1, M, 1, −M, 1, −M}*(1+j)/sqrt(2), and the sqrt ( )represents square root, and wherein the preset M sequence is a binarysequence of a length having 15 bits and is defined as M={−1, −1, −1, 1,1, 1, −1, 1, 1, 1, −1, 1, 1, −1, 1}.
 2. The method of claim 1, whereinthe sequence of {M, −1, M, −1, −M, −1, M, 0, −M, 1, M, 1, −M, 1, −M, 0,−M, 1, −M, 1, M, 1, −M, 0, −M, 1, M, 1, −M, 1, −M}*(1+j)/sqrt(2) isarranged in a 8-tone interval from the lowest tone with tone index −1016to the highest tone with tone index +1016, and wherein in the sequenceof {M, −1, M, −1, −M, −1, M, 0, −M, 1, M, 1, −M, 1, −M, 0, −M, 1, −M, 1,M, 1, −M, 0, −M, 1, M, 1, −M, 1, −M}*(1+j)/sqrt(2), elementscorresponding to tone index −8, 8, −1016 and 1016 are nulled.
 3. Themethod of claim 1, wherein the transmitting apparatus selects a firstfrequency tone interval or a second frequency tone interval andconfigures the STF signal according to the selected frequency toneinterval.
 4. The method of claim 3, when the PPDU is an uplink MU PPDUcorresponding to a trigger frame received from an AP, the firstfrequency tone interval is selected.
 5. The method of claim 3, whereinthe first frequency tone interval is 8, and the second frequency toneinterval is
 16. 6. The method of claim 1, wherein the plurality offrequency bands include a second frequency band narrower that the firstfrequency band, the method further comprising generating an STF signalcorresponding to the second frequency band using a sequence of {M, −1,M, −1, −M, −1, M, 0, −M, 1, M, 1, −M, 1, −M}*(1+j)/sqrt(2).
 7. Themethod of claim 1, wherein the first frequency band is 80+80 MHz or 160MHz, and the second frequency band is 80 MHz.
 8. The method of claim 7,wherein the STF signal corresponding to the first frequency band isgenerated based on a sequence for a primary channel and a sequence for asecondary channel, and wherein the sequence for the secondary channel isreplaced with the sequence for the primary channel.
 9. The method ofclaim 8, wherein the primary channel and the secondary channel support aplurality of frequency resource units (RUs), and wherein the sequencefor the secondary channel includes a sequence corresponding to a center26-RU and a 996-RU supported by the secondary channel, and wherein thesequence for the primary channel includes a sequence corresponding to acenter 26-RU and a 996-RU supported by the primary channel, and whereinthe center 26-RU is a center frequency RU composed of 26 subcarriers,and the 996-RU is a frequency RU composed of 996 subcarriers.
 10. Themethod of claim 1, wherein wherein the STF signal is used to enhanceautomatic gain control (AGC) estimation in a multiple input multipleoutput (MIMO) transmission.
 11. A transmitting apparatus of transmittinga training signal in a wireless LAN system supporting a plurality offrequency bands, the transmitting apparatus comprising: a transceiverthat transmits and receives a radio signal; and a processor configuredto control the transceiver, and wherein the processor further configureto: generate a short training field (STF) signal corresponding to afirst frequency band of the plurality of frequency bands; and transmit aPPDU (physical protocol data unit) including the STF signal to areceiving apparatus, and wherein the STF signal corresponding to thefirst frequency band is generated based on a sequence in which a presetM sequence is repeated, and wherein the repeated sequence is defined as{M, −1, M, −1, −M, −1, M, 0, −M, 1, M, 1, −M, 1, −M, 0, −M, 1, −M, 1, M,1, −M, 0, −M, 1, M, 1, −M, 1, −M}*(1+j)/sqrt(2), and the sqrt ( )represents square root, and wherein the preset M sequence is a binarysequence of a length having 15 bits and is defined as M={−1, −1, −1, 1,1, 1, −1, 1, 1, 1, −1, 1, 1, −1, 1}.